Heat-resistant and moisture-resistant water-based adhesive applied to polarizing sheet, preparation method and application

Abstract

The application provides a heat-resistant and moisture-resistant water-based adhesive applied to a polarizing sheet, a preparation method and application, and belongs to the technical field of polarizing sheets. The water adhesive is prepared by reacting acetyl acetyl-modified polyvinyl alcohol with a diacylhydrazine type and a glyoxylate type crosslinking agent under the regulation of various metal ions, is attached between a phase difference compensation film and a polarizing sheet base film (element), has excellent water vapor barrier effect and heat resistance, and can also improve the anti-blue light effect.

Description

Technical Field

[0001] This invention belongs to the field of polarizer technology, and relates to a heat- and moisture-resistant water-based adhesive for use in polarizers, its preparation method, and its application. Background Technology

[0002] In today's high-tech era, electronic devices are used in an increasingly wide range of applications, from everyday smartphones and tablets to high-end medical imaging equipment and aerospace display systems. Liquid crystal displays (LCDs) have become an indispensable visual interface. As a crucial component of LCDs, the performance of the polarizer directly determines the quality of the display. Especially under extreme environmental conditions, the polarizer's resistance to moisture and heat is of paramount importance.

[0003] With the intensification of global climate change, electronic devices face increasingly severe environmental challenges. High temperatures can cause polarizer materials to deform, affecting their optical performance, while humidity can cause material expansion or corrosion, thus impacting the stability and reliability of electronic devices. Therefore, improving the moisture and heat resistance of polarizers has become a pressing technical challenge for the electronics industry.

[0004] As users of electronic devices become increasingly demanding in their expectations for display quality, this includes not only color accuracy and contrast, but also stable display performance under various environmental conditions. Whether in scorching deserts, humid rainforests, or high-altitude regions with extreme temperature variations, polarizers need to exhibit superior moisture and heat resistance to ensure that devices function properly under diverse conditions.

[0005] To meet these requirements, improving the moisture and heat resistance of polarizers and enhancing the moisture and heat resistance of water-based adhesives used for bonding phase retardation films and elements is an effective approach.

[0006] This invention proposes using dihydrazide-based substances to react and crosslink with acetylated polyvinyl alcohol to improve the moisture and heat resistance of water-based adhesives. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a heat- and moisture-resistant water-based adhesive for polarizing films, its preparation method, and its application, thereby improving the poor moisture and heat resistance of existing polarizing films and producing high-quality water-based adhesives for high-performance polarizing films used in the manufacture of novel displays.

[0008] The present invention provides a method for preparing a water-based adhesive with moisture and heat resistance. There are no strict regulations. First, acetylated polyvinyl alcohol is dissolved in water, then metal ions are added, and then crosslinking agents are added in sequence.

[0009] The present invention adopts the following technical solution:

[0010] A method for preparing a water-based adhesive with moisture and heat resistance includes the following steps:

[0011] First, dissolve acetylated polyvinyl alcohol in water, then add metal ions, and finally add the crosslinking agent solution in sequence.

[0012] Furthermore, the acetylated polyvinyl alcohol is dissolved in water at a heating temperature of 85~100 ℃, preferably 90~98 ℃, more preferably 92~94 ℃; the stirring time is preferably 2~6 h, more preferably 3~4 h.

[0013] Furthermore, after acetylated polyvinyl alcohol is dissolved in water, an acetylated polyvinyl alcohol solution is obtained, wherein the mass ratio of acetylated polyvinyl alcohol to water is 0.1~20:78.

[0014] Furthermore, when the metal ions are added to the acetylated polyvinyl alcohol solution, the heating temperature needs to be lowered to below 40 °C, preferably 30~38 °C, more preferably 32~35 °C, and the stirring time is preferably 0.5~1 h.

[0015] Furthermore, the metal ions included may be one, two, three, four, five, or six of the following: zinc ions, zirconium ions, copper ions, cobalt ions, sodium ions, and calcium ions.

[0016] Furthermore, the metal ions are zinc ions, zirconium ions, and copper ions; preferably, the zinc ions are derived from zinc chloride, the zirconium ions are derived from zirconium chloride, and the copper ions are derived from copper chloride.

[0017] Further, the mass ratio of zinc ions to acetylated polyvinyl alcohol is 0.0001:4, 0.0005:4, 0.001:4, 0.005:4, 0.01:4, 0.02:4, 0.05:4, 0.1:4, 0.5:4, or 1:4, and the mass ratio of zirconium ions to acetylated polyvinyl alcohol is 0.0001:4, 0.0005:4, 0.00... The mass ratio of copper ions to acetylated polyvinyl alcohol is 0.0001:4, 0.005:4, 0.01:4, 0.02:4, 0.05:4, 0.1:4, 0.5:4, or 1:4, with the ratio being 1:4. The mass ratio of cobalt ions to acetylated polyvinyl alcohol is 0.0001:4, 0.0005:4, 0.001:4, 0.005:4, 0.01:4, 0.02:4, 0.05:4, 0.1:4, 0.5:4, or 1:4, and the mass ratio of sodium ions to acetylated polyvinyl alcohol is 0.0001:4, 0.0005:4, 0.001:4. The mass ratio of calcium ions to acetylated polyvinyl alcohol is 0.0001:4, 0.0005:4, 0.001:4, 0.005:4, 0.1:4, 0.5:4, or 1:4, and the mass ratio of calcium ions to acetylated polyvinyl alcohol is 0.0001:4, 0.0005:4, 0.001:4, 0.005:4, 0.01:4, 0.02:4, 0.05:4, 0.1:4, 0.5:4, or 1:4.

[0018] Furthermore, glyoxylate is added before adding the crosslinking agent solution, with the mass ratio of glyoxylate to acetylated polyvinyl alcohol being 0.1:4, 0.5:4, 1:4, 1.5:4, 2:4, 2.5:4, or 3:4. The mixture is stirred for 0.5 to 1 hour (the stirring time should be specified in the examples), and then the dihydrazide crosslinking agent solution is added and stirred for 5 to 10 seconds. The mass ratio of the dihydrazide crosslinking agent to acetylated polyvinyl alcohol is 0.01:4, 0.02:4, 0.05:4, 0.1:4, 0.5:4, 1:4, 1.5:4, 2:4, 2.5:4, or 3:4. In the solution of dihydrazide crosslinking agent, the mass ratio of dihydrazide crosslinking agent to water is 0.1:15.6, 0.2:15.6, 0.38:15.6, 0.5:15.6, 1:15.6, 1.5:15.6, 2:15.6, 2.5:15.6 or 3:15.6.

[0019] Aqueous adhesives prepared by any of the methods described above.

[0020] The application of adhesives as described above in polarizers.

[0021] The acetylated polyvinyl alcohol is dissolved in water. There are no strict requirements for the heating temperature and stirring time. The preferred heating temperature is 85-100 °C, more preferably 90-98 °C, and even more preferably 92-94 °C. The preferred stirring time is 2-6 h, more preferably 3-4 h.

[0022] When the metal ions are added to dissolve polyvinyl alcohol, the heating temperature needs to be lowered to below 40 ℃, preferably 30~38 ℃, more preferably 32~35 ℃. From the perspective of affecting the uniformity of the solution, the stirring time is preferably within 0.5~1 h.

[0023] The main metal ions involved include zinc ions, zirconium ions, copper ions, cobalt ions, sodium ions, and calcium ions.

[0024] The phase difference compensation films mainly include one or more of the following: cellulose triacetate phase difference film (TAC), polymethyl methacrylate phase difference film (PMMA), and cyclic olefin polymer phase difference film (COP).

[0025] When adding the crosslinking agent to the water-based adhesive, there are no strict requirements on the heating temperature and stirring time. The temperature should be the same as in the previous step. When adding the crosslinking agent, glyoxylate should be added first, and the mixture should be stirred for 0.5 to 1 hour before adding the dihydrazide crosslinking agent. The adhesive should be bonded immediately after stirring for 5 to 10 seconds.

[0026] Advantages and positive effects:

[0027] To improve the poor moisture and heat resistance of existing polarizers, a high-quality water-based adhesive for use in the manufacture of new displays was produced, which is designed to improve the moisture and heat resistance of existing polarizers. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view of the optical laminate according to an embodiment of the invention;

[0029] Figure 2 It is the chemical formula of acetylated polyvinyl alcohol;

[0030] Figure 3 It is the chemical formula structure of an acylhydrazine compound;

[0031] Figure 4 It is the chemical reaction mechanism between acetylated polyvinyl alcohol and acylhydrazine compounds;

[0032] Figure 5 These are the melt profiles of the aqueous adhesives in all embodiments and comparative examples;

[0033] Figure 6 These are the crystallization curves of the aqueous adhesives in all embodiments and comparative examples;

[0034] Figure 7These are the MSE-FID nuclear magnetic resonance decay curves of all embodiments and comparative examples of the aqueous adhesives;

[0035] Figure 8 These are the mechanical curves of the water-based adhesives in Examples 1 and 2 and Comparative Example 1;

[0036] Figure 9 This is a graph showing the relationship between polarization efficiency and time for optical laminates obtained by bonding Examples 1, 2 and Comparative Example 3 under double 85 conditions.

[0037] Figure labeling: 1 element, 2 water-based adhesive, 3 phase difference compensation film. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, the invention adopts the following technical solution:

[0039] Figure 1 This is a cross-sectional view of the optical laminate according to an embodiment of the invention. In the figure, 1 represents the element, 3 represents the phase difference compensation film, and 2 represents the aqueous adhesive. The aqueous adhesive 2 is used to bond the element 1 and the phase difference compensation film 3 together. The upper and lower surfaces of the element (polarizer base film) 1 are bonded to the phase difference compensation film 3 using the aqueous adhesive 2. Roller pressing is used to evenly distribute the aqueous adhesive between the two films. The thickness of the adhesive layer after curing is approximately 200 nm. The film is then placed in an 80°C forced-air drying oven to obtain a polarizer without the protective film, i.e., the optical laminate.

[0040] Figure 2 It is the chemical formula of acetylated polyvinyl alcohol. Figure 3 It is the chemical formula structure of an acylhydrazine compound, where R can be any group. Figure 4 The mechanism involves the chemical reaction between acetylated polyvinyl alcohol and acylhydrazine compounds. The carbonyl group at the end of the side chain of acetylated polyvinyl alcohol reacts with the amino group at the end of the acylhydrazine compound to form an amide bond.

[0041] Example 1

[0042] A. Preparation of acetylated polyvinyl alcohol solution and adipic acid dihydrazide solution

[0043] Weigh out 78 parts by weight of water and 4 parts by weight of acetylated polyvinyl alcohol (Mitsubishi Chemical Corporation, GOHSENX™ Z-200) powder according to the formula, and dissolve them in a reaction vessel at 94°C to obtain an acetylated polyvinyl alcohol solution. Weigh out 0.38 parts by weight of adipic acid dihydrazide and 15.6 parts by weight of water according to the formula, and dissolve them in another reaction vessel at room temperature to obtain an adipic acid dihydrazide solution.

[0044] B. Preparation and Use of Water-Based Adhesives

[0045] According to the formula, at 35°C, 0.01 parts by mass of zinc chloride, 0.018 parts by mass of zirconium chloride, and 0.001 parts by mass of copper chloride were added sequentially to an acetylated polyvinyl alcohol solution. After dissolving and heating with stirring for 1 hour, 1.9 parts by mass of sodium glyoxylate were added. After dissolving and heating with stirring for 1 hour, an adipic acid dihydrazide solution was added and stirred for 7 seconds to obtain a heat- and moisture-resistant water-based adhesive. Immediately follow the instructions... Figure 1 The method of bonding the element (provided by Anhui Wanwei Group Co., Ltd.) with the cellulose triacetate phase difference compensation film (TAC, provided by Anhui Wanwei Group Co., Ltd.) is as follows.

[0046] Example 2

[0047] A. Preparation of acetylated polyvinyl alcohol solution and succinic dihydrazide solution

[0048] Weigh out 78 parts by weight of water and 4 parts by weight of acetylated polyvinyl alcohol (Mitsubishi Chemical Corporation, GOHSENX™ Z-200) powder according to the formula, and dissolve them in a reaction vessel at 94°C to obtain an acetylated polyvinyl alcohol solution. Weigh out 0.33 parts by weight of succinic dihydrazide and 15.6 parts by weight of water according to the formula, and dissolve them in another reaction vessel at room temperature to obtain a succinic dihydrazide solution.

[0049] B. Preparation and Use of Water-Based Adhesives

[0050] According to the formula, at 35°C, 0.01 parts by mass of zinc chloride, 0.018 parts by mass of zirconium chloride, and 0.01 parts by mass of copper chloride were added sequentially to an acetylated polyvinyl alcohol solution. After dissolving and heating with stirring for 1 hour, 1.9 parts by mass of sodium glyoxylate were added. After dissolving and heating with stirring for 1 hour, a dihydrazide solution was added and stirred for 7 seconds to obtain a heat- and moisture-resistant water-based adhesive. Immediately follow the instructions... Figure 1 The method of bonding the element to the cellulose triacetate phase difference compensation membrane (TAC, provided by Anhui Wanwei Group Co., Ltd.) is as follows.

[0051] Comparative Example 1

[0052] A. Preparation of acetylated polyvinyl alcohol solution

[0053] Weigh out 93 parts by weight of water and 4.9 parts by weight of acetylated polyvinyl alcohol (Mitsubishi Chemical Corporation, GOHSENX™ Z-200) powder according to the formula, and dissolve them in a reaction vessel at 94°C.

[0054] B. Preparation and Use of Water-Based Adhesives

[0055] According to the formula, at 35°C, 0.023 parts by mass of zinc chloride were added to an acetylated polyvinyl alcohol solution, and after dissolving and heating for 1 hour, 2.07 parts by mass of sodium glyoxylate were added, and after dissolving and heating with stirring for 1 hour, the solution was dissolved. Figure 1 The method of bonding the element to the phase difference compensation membrane of cellulose triacetate (provided by Anhui Wanwei Group Co., Ltd.)

[0056] Comparative Example 2

[0057] A. Preparation of acetylated polyvinyl alcohol solution

[0058] Weigh out 93 parts by weight of water and 4.9 parts by weight of acetylated polyvinyl alcohol (Mitsubishi Chemical Corporation, GOHSENX™ Z-200) powder according to the formula, and dissolve them in a reaction vessel at 94°C.

[0059] B. Preparation and Use of Water-Based Adhesives

[0060] According to the formula, at 35°C, 0.04 parts by mass of zirconium chloride were added to an acetylated polyvinyl alcohol solution, and after dissolution and heating for 1 h, 2.06 parts by mass of sodium glyoxylate were added, and after dissolution and heating with stirring for 1 h, the solution was dissolved. Figure 1 The method of bonding the element to the phase difference compensation membrane of cellulose triacetate (provided by Anhui Wanwei Group Co., Ltd.)

[0061] Comparative Example 3

[0062] A. Preparation of acetylated polyvinyl alcohol solution

[0063] Weigh out 93 parts by weight of water and 4.9 parts by weight of acetylated polyvinyl alcohol (Mitsubishi Chemical Corporation, GOHSENX™ Z-200) powder according to the formula, and dissolve them in a reaction vessel at 94°C.

[0064] B. Preparation and Use of Water-Based Adhesives

[0065] According to the formula, 2.1 parts by weight of sodium glyoxylate were added to an acetylated polyvinyl alcohol solution at 35°C, and the solution was dissolved and stirred for 1 hour. Figure 1 The method of bonding the element to the phase difference compensation membrane of cellulose triacetate (provided by Anhui Wanwei Group Co., Ltd.)

[0066] The aqueous adhesive prepared in the examples was used to bond the most important elements in the polarizer to the retardation film. Using this aqueous adhesive improved the polarizer's resistance to damp heat.

[0067] By comparing the above examples and comparative examples, it can be concluded that the water-based adhesive prepared in the examples has better moisture and heat resistance. Under high humidity and high heat conditions, the polarization efficiency, an important indicator of polarizers, decreases more slowly. This is because the water-based adhesive prepared in the examples has a high degree of crosslinking, forming a denser crosslinking network that effectively inhibits the invasion of water molecules. Furthermore, compared with the comparative examples, it has lower cohesion, resulting in polarizers that are more resistant to bending.

[0068] For product-related tests, please refer to... Figures 5 to 9 The testing method is as follows:

[0069] Thermal analysis of water-based adhesives: The water-based adhesives prepared in all examples and comparative examples were poured into petri dishes and placed in an 80°C forced-air oven until the film was dried, which took 5 h. The film thickness ranged from 60 to 100 μm. The film thickness was measured by differential scanning calorimetry.

[0070] Transverse relaxation time analysis of waterborne adhesives: The waterborne adhesives prepared in all examples and comparative examples were poured into petri dishes and placed in an 80 °C forced-air oven until the film was dried, which took 5 h. The film thickness ranged from 60 to 100 μm. The film was detected by low-field nuclear magnetic resonance.

[0071] Mechanical curve measurement of water-based adhesives: The water-based adhesives prepared in Examples 1 and 2 and Comparative Example 1 were poured into petri dishes and placed in an 80 °C forced-air oven until the film was dried, which took 5 h. The film thickness ranged from 60 to 100 μm. The film was tested using a universal tensile tester at a speed of 60 mm / min, a force capacity of 2000 N, and an initial load of 0.05 N.

[0072] Analysis of the moisture and heat resistance of water-based adhesives: The water-based adhesives prepared in Examples 1 and 2 and Comparative Example 3 were analyzed according to... Figure 1 The polarizer was bonded to the element and the cellulose triacetate phase difference compensation film (provided by Anhui Wanwei Group Co., Ltd.). The resulting polarizer without pressure-sensitive adhesive and protective film was placed in a constant temperature and humidity chamber at 85 ℃ and 85% humidity. Under the harsh conditions of 85 ℃ and 85% humidity for a period of time, including 100 h, 209 h, and 260 h, the polarization efficiency and other optical indicators were measured using a phase difference meter.

[0073] All examples and comparative examples were analyzed by differential scanning calorimetry, as shown in Figure 5. Figure 6The melting and crystallization curves show that the peak areas of both the melting and crystallization peaks of the water-based adhesive decrease after the addition of dihydrazide compounds. These melting and crystallization characteristic values ​​directly reflect the influence of dihydrazide compounds and metal ions on the crystallization state of the water-based adhesive. After crosslinking of acetylated polyvinyl alcohol, the molecular chains become entangled, restricting their mobility and reducing their regularity. This leads to a decrease in crystallization ability, requiring lower temperatures for crystallization, resulting in thinner crystals and a continuous decrease in overall crystallinity. In other words, the addition of dihydrazide compounds and metal ions increases the degree of crosslinking in the water-based adhesive, forming a denser crosslinked network.

[0074] All embodiments and comparative examples were analyzed by low-field nuclear magnetic resonance imaging. Figure 7 It is observed that the addition of dihydrazide compounds to aqueous adhesives results in a rapid decay of the free-induction decay signal. During polymer crosslinking, as the degree of crosslinking increases, the degrees of freedom of the molecular chains decrease, and the overall rigidity of the material increases. This affects the distribution of transverse relaxation time. Molecular chain segments in rigid chains are less prone to rotation, and their interactions are stronger, leading to faster energy exchange and shorter transverse relaxation times. Aqueous adhesives containing dihydrazide compounds have a higher proportion of rigid components compared to the control group.

[0075] Examples 1 and 2, and Comparative Example 1, were tested using a universal tensile testing machine. Figure 8 It can be seen that the tensile strength and elongation at break of water-based adhesives decreased after the addition of dihydrazide compounds. This is because the rigidity of the cross-linked network increased, making the material more prone to sudden fracture rather than continuous plastic deformation under stress, thus reducing the elongation at break. However, the tensile strength of the material was not significantly enhanced. Compared with Comparative Example 1, the cohesive force of the material was smaller, and the polarizer after lamination was less likely to curl.

[0076] Optical laminates placed in a constant temperature and humidity chamber for different durations were detected using a phase difference meter. Figure 9 It is known that using an aqueous adhesive containing dihydrazide compounds to bond the optical laminate of TAC and Element has a slower failure rate, and Example 1 has better moisture and heat resistance.

Claims

1. A method for preparing a heat- and moisture-resistant water-based adhesive for use in polarizing films, characterized in that, Includes the following steps: First, acetylated polyvinyl alcohol is dissolved in water, then metal ions are added, followed by the addition of a crosslinking agent solution in sequence; the acetylated polyvinyl alcohol is dissolved in water at a heating temperature of 85~100 ℃; the stirring time is 2~6 h. After acetylated polyvinyl alcohol is dissolved in water, an acetylated polyvinyl alcohol solution is obtained, with the mass ratio of acetylated polyvinyl alcohol to water being 0.1~20:

78. When the metal ions are added to the acetylated polyvinyl alcohol solution, the heating temperature needs to be lowered to below 40 °C. The metal ions mentioned are zinc ions, zirconium ions, and copper ions; zinc ions are derived from zinc chloride, zirconium ions are derived from zirconium chloride, and copper ions are derived from copper chloride. The mass ratio of zinc ions to acetylated polyvinyl alcohol is 0.0005~1:4, the mass ratio of zirconium ions to acetylated polyvinyl alcohol is 0.0005~1:4, and the mass ratio of copper ions to acetylated polyvinyl alcohol is 0.0005~1:

4. Before adding the crosslinking agent solution, glyoxylate is added first, with a mass ratio of glyoxylate to acetylated polyvinyl alcohol of 0.1~3:

4. After stirring for 0.5~1 h, the diacylhydrazine crosslinking agent solution is added, and the mixture is stirred for 5~10 s. The mass ratio of diacylhydrazine crosslinking agent to acetylated polyvinyl alcohol is 0.01~3:

4. The diacylhydrazine crosslinking agent is adipic acid diacylhydrazine. In the diacylhydrazine crosslinking agent solution, the mass ratio of diacylhydrazine crosslinking agent to water is 0.1~2:15.

6.

2. The aqueous adhesive prepared by the method of claim 1.

3. The application of the adhesive according to claim 2 in polarizers.

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